Conventionally, there have been used batteries, such as a nickel-hydrogen storage battery and a lithium-ion storage battery, as a power supply source for driving an electric vehicle and a hybrid vehicle. In order to use those batteries safely, and without being deteriorated, a usable voltage range is previously set in the batteries. There is used a control device which obtains a maximum charge/discharge current of the battery without deviation from the voltage range and performs charge/discharge control of the battery based on the maximum charge/discharge current.
The following PTL 1 discloses a control device which obtains a maximum current during charge and controls charge of a power storage device. The control device obtains a battery voltage (a positive electrode potential and a negative electrode potential) during no-load based on a charge state (SOC: State Of Charge) of a battery as a power storage device, further obtains an internal resistance of the battery based on a temperature of the battery, and calculates a maximum current during charge using them.